former island, has lost the tail, which is a prominent feature of the closely allied P. Machaon. Facts of a similar nature to those now brought forward would no doubt be found to occur in other groups of insects, were local faunas carefully studied in relation to those of the surrounding countries; and they seem to indicate that climate and other physical causes have, in some cases, a very powerful effect in modifying specific form and colour, and thus directly aid in producing the endless variety of nature. _Mimicry._ Having fully discussed this subject in the preceding essay, I have only to adduce such illustrations of it, as are furnished by the Eastern Papilionidae, and to show their bearing upon the phenomena of variation already mentioned. As in America, so in the Old World, species of Danaidae are the objects which the other families most often imitate. But besides these, some genera of Morphidae and one section of the genus Papilio are also less frequently copied. Many species of Papilio mimic other species of these three groups so closely that they are undistinguishable when on the wing; and in every case the pairs which resemble each other inhabit the same locality. The following list exhibits the most important and best marked cases of mimicry which occur among the Papilionidae of the Malayan region and India:-- Mimickers. Species mimicked. Common habitat. DANAIDAE. 1. Papilio paradoxa Euploea Midamus } Sumatra, &c. (male & female) (male & female) } 2. P. Caunus E. Rhadamanthus Borneo and Sumatra. 3. P. Thule Danais sobrina New Guinea. 4. P. Macareus D. Aglaia Malacca, Java 5. Papilio Agestor Danais Tytia Northern India. 6. P. Idaeoides Hestia Leuconoe Philippines. 7. P. Delessertii Ideopsis daos Penang. MORPHIDAE. 8. P. Pandion Drusilla bioculata New Guinea (female) PAPILIO (POLYDORUS- and COON-groups). 9. P. Pammon (Romulus, Papilio Hector India. female) 10. P. Theseus, var. P. Antiphus Sumatra, Borneo. (female) 11. P. Theseus, var. P. Diphilus Sumatra, Java. (female) 12. P. Memnon, var. P. Coon Sumatra. (Achates, female) 13. P. Androgeus, var. P. Doubledayi Northern India. (Achates, female) 14. P. Oenomaus P. Liris Timor. (female)